In recent years, thin-film solar batteries formed by plasma CVD method using a gas as a raw material have been attracting attention. Examples of the thin-film solar batteries include silicon-based thin-film solar batteries formed of a silicon-based thin film, CIS or CIGS compound thin-film solar batteries, and the like, and development and production expansion are being promoted.
These thin-film solar batteries are formed by stacking a semiconductor film or an electrode film on a substrate by plasma CVD, sputtering, vacuum deposition, or the like. Since the thin-film solar battery has a thin semiconductor layer sandwiched between two electrodes, a short circuit is likely to occur between the electrodes due to a pin hole in the semiconductor layer, and thereby power generation characteristics are deteriorated. For the purpose of recovering such characteristics of the thin-film solar battery, Japanese Patent Laying-Open No. 2000-323738 describes an invention related to a reverse bias processing apparatus for a solar battery module in which a reverse bias voltage is applied between electrodes of solar battery cells to remove a short-circuited portion (pin hole).
Further, the reverse bias processing apparatus for a solar battery module described in Japanese Patent Laying-Open No. 2000-323738 is characterized by having probes in plural stages contacting electrodes of solar battery cells in three or more stages adjacent with one another, lifting and lowering means integrally lifting and lowering the probes in plural stages, and a switch selecting, from among the probes in plural stages, a pair of probes for applying a reverse bias voltage between electrodes of an arbitrary pair of adjacent solar battery cells. It is described that, since reverse bias processing can be performed on solar battery cells in plural stages by lowering the probes to bring them into contact with the electrodes of the solar battery cells and then switching the switch, the number of operations for lowering the probes, which is most time consuming, can be significantly reduced when compared with a conventional case, and the efficiency of the entire reverse bias processing can be improved.
FIGS. 5 and 6 are views for describing a reverse bias processing apparatus for conventional photoelectric conversion devices. FIG. 5 is a schematic cross sectional view of a plurality of conventional photoelectric conversion devices connected in series, and FIG. 6 shows an equivalent circuit thereof.
As shown in FIG. 5, a surface electrode 107 made of a transparent conductive film such as SnO2, a semiconductor layer 108 including a photoelectric conversion layer, and a rear surface electrode 104 made of a metal and a transparent electrode are stacked on a transparent insulating substrate 106 such as glass. Surface electrode 107, semiconductor layer 108, and rear surface electrode 104 are partially removed, and electrical connection is established between a surface electrode 107a and a rear surface electrode 104b, between a surface electrode 107b and a rear surface electrode 104c, between a surface electrode 107c and a rear surface electrode 104d, between a surface electrode 107d and a rear surface electrode 104e, between a surface electrode 107e and a rear surface electrode 104f, and between a surface electrode 107f and a rear surface electrode 104g, of adjacent photoelectric conversion devices. Thereby, photoelectric conversion devices 103a to 103f are connected in series.
The equivalent circuit of FIG. 6 shows photoelectric conversion devices 103a to 103f and rear surface electrodes 104a to 104g. Herein, according to the apparatus of Japanese Patent Laying-Open No. 2000-323738, a reverse bias voltage is applied between rear surface electrode 104a and rear surface electrode 104b, that is, to photoelectric conversion device 103a, to perform reverse bias processing, and then the switch is used to apply the reverse bias voltage between rear surface electrode 104b and rear surface electrode 104c, that is, to photoelectric conversion device 103b, to perform reverse bias processing. Thereafter, reverse bias processing is sequentially performed up to photoelectric conversion device 103f.     Patent Document 1: Japanese Patent Laying-Open No. 2000-323738